Leaders of Russia, the United States and France on Thursday called for an immediate cessation of hostilities between countries involved in the armed conflict in the Nagorno-Karabakh region, according to the Kremlin.

In a joint statement published by the Kremlin, Russian President Vladimir Putin, U.S. President Donald Trump and French President Emmanuel Macron, representing the Organization for Security and Cooperation in Europe (OSCE) Minsk Group Co-Chairs countries, condemn in the strongest terms the escalation of violence taking place on the contact line in the Nagorno-Karabakh region.

"We mourn the victims and express our condolences to the families of those killed and wounded," it read.

"We also call on the leaders of Armenia and Azerbaijan to immediately undertake commitments in good faith and without setting preconditions to resume negotiations on the essence of the settlement with the assistance of the OSCE Minsk Group Co-Chairs," said the statement.

Armenia and Azerbaijan have been at loggerheads over the mountainous region of Nagorno-Karabakh since 1988. Peace talks have been held since 1994 when a ceasefire was reached, but there have been occasional minor clashes along the border.

A new round of armed conflict broke out Sunday morning along the contact line of the Nagorno-Karabakh region. The clashes, which are still going on, have reportedly caused heavy casualties and equipment loss.